Method and apparatus for providing a marker for adaptive formatting via a self-servowrite process

ABSTRACT

A method and apparatus for providing a marker at the end of the adaptive self-servowrite process for adaptive formatting via the self-servowrite process. The mark is used later in the drive manufacturing process to identify the number of tracks written on the surface and thus determine the appropriate format to use in the drive.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to magnetic storage systems, and moreparticularly to a method and apparatus for providing a marker foradaptive formatting via a self-servowrite process.

2. Description of Related Art

Magnetic recording systems that utilize magnetic disk and tape drivesconstitute the main form of data storage and retrieval in present-daycomputer and data processing systems. In the recording process,information is written and stored as magnetization patterns on themagnetic recording medium. Scanning a write head over the medium andenergizing the write head with appropriate current waveforms accomplishthis recording process. In a read-back process, scanning a read sensorover the medium retrieves the stored information. This read sensorintercepts magnetic flux from the magnetization patterns on therecording medium and converts the magnetic flux into electrical signals,which are then detected and decoded.

Continually increasing storage capacities in hard disk drives requireinnovations in magnetic hard disk drive design. One area of concern isthe need for precision manufacturing. Hard disk drives store data inconcentric tracks, and the density of those tracks has increased alongwith linear bit density over time. To read and write data, the diskdrive head must remain accurately centered on a selected track. Attoday's track densities, the head must stay centered on the narrowtracks to within a staggering tolerance of one-millionth of an inch orless. To achieve this level of precision, the head must read positioninformation along the track that is permanently written onto the disk.The position information is used by a precision electronics controlsystem that servos the recording head onto the track.

The process by which the position information is written onto the disksis referred to as servowriting and is performed only once—during themanufacture of the device. The information remains on the disk for thelife of the product. The machines that write these servo patterns—calledservowriters—must be very precise instruments.

Traditional servo writing has been performed in a clean room environmentwith external sensors invading the head disk assembly to provide theprecise angular and radial position information to write the servopatterns. For example, an external clock head was typically disposed onthe disk outer diameter. This provided the angular information used towrite the servo patterns. While such instruments have been satisfactoryto set the patterns in the past, today's increased track density hasbecome so precise that the mechanical vibration of the file (relative tothese external sensors) as well as other factors can limit the accuracyor increase the complexity of these systems.

A more precise servowriting technology has been developed to overcomethe problems associated with the traditional servo writing process. Thenew approach uses servowrite self-timing technology. The clock headsused in traditional servowriters is replaced with an electronicnon-invasive process to create the time alignment of servo patternsbetween adjacent tracks.

A digital signal processor executing a predetermined mathematicalalgorithm is used to accomplish the time alignment. In this method, thehard disk drive generates its own timing information while the drive isbeing servo written, using only the product data head. The patterns areself-propagated and aligned by a digital signal processor (DSP),resulting in a substantial increase in time alignment over otherservowriting methods and significantly improved performance, quality,and reliability.

The self-servowrite process eliminates mechanical vibrations associatedwith external clocking while significantly improving servo pattern timealignment. This results in fewer servo errors—and thus fewer writeinhibits—to improve drive performance. The improved time alignment alsoenables a reduction in the size of the sector fields, thereby increasingdata capacity. The self-servowrite process also eliminates externalinvasive clock heads, which can damage the drives during manufacture.Thus, the drive leaves the manufacturing facility with a clean bill ofhealth, having been assembled and tested in a manner to preserve itsquality and integrity.

Improved time alignment in the servo pattern fields means fewer servosubstitutions, which further increases data reliability. Additionally,the self-servowrite process includes in-process algorithms to detect andcorrect servowriter errors as they occur. The result of this monitoringof the servowriting process (catching and correcting errors “on thefly”) is that disk drives are servo written with fewer errors. Thisimproves product quality and makes the manufacturing process moreefficient—all of which can reduce the cost for end users.

Nevertheless, for adaptive formatting, wherein the number of availabledata tracks can vary, the number of tracks to be formatted must bedetermined. Currently, determining the number of available tracks fromthe self servowrite process requires a trial and error process orrequires that the track count be sent ahead from the servowriter to thefunction test station.

It can then be seen that there is a need for a method and apparatus foridentifying the number of tracks written on the surface and thusdetermine the appropriate format to use in the drive.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesa method and apparatus for providing a marker for adaptive formattingvia a self-servowrite process.

The present invention solves the above-described problems by providing amarker at the end of the adaptive self-servowrite process that can beused to identify the number of tracks written on the surface and thusdetermine the appropriate format to use in the drive.

A method in accordance with the principles of the present inventionincludes performing an adaptive self-servowrite process to write tracksto a recording surface, writing a marker at a predetermined location onthe recording surface, the marker indicating the number of trackswritten during the adaptive self-servowrite process, prior toformatting, locating the marker, processing the marker to determine anumber of tracks written during the adaptive self-servowrite process,ascertaining an appropriate formatting based upon the determined numberof tracks indicated by the marker and formatting the recording surfaceaccording to the ascertained format.

In another embodiment of the present invention, a servo writtenrecording medium is provided. The servo written recording mediumincludes a number of tracks written during an adaptive self-servowriteprocess and a marker disposed at a predetermined location on therecording surface, wherein the marker indicates the number of trackswritten during the adaptive self-servowrite process.

In another embodiment of the present invention, a storage system isprovided. The storage system includes a moveable storage medium having arecording surface for storing data thereon, a motor for causing movementof the moveable storage medium, an actuator assembly having an actuatorarm and a sensor disposed at a distal end of the actuator arm, thesensor for reading and writing data on the disk, a servo controller,operatively coupled to the actuator assembly and sensor, the servocontroller providing a drive signal to the actuator assembly for movingthe actuator arm relative to the recording medium, the servo controllerperforming an adaptive self-servowrite process to write a number oftracks to a recording surface, writing a marker at a predeterminedlocation on the recording surface, the marker indicating the number oftracks written during the adaptive self-servowrite process, prior toformatting, locating the marker, processing the marker to determinenumber of tracks written during the adaptive self-servowrite process,ascertaining an appropriate formatting based upon the determined numberof tracks indicated by the marker and formatting the recording surfaceaccording to the ascertained format.

In another embodiment of the present invention, an article ofmanufacture comprising a program storage medium readable by a computeris provided. The medium tangibly embodies one or more programs ofinstructions executable by the computer to perform a method forproviding adaptive formatting via a self-servowrite process, the methodincludes performing an adaptive self-servowrite process to write tracksto a recording surface, writing a marker at a predetermined location onthe recording surface, the marker indicating the number of trackswritten during the adaptive self-servowrite process, prior toformatting, locating the marker, processing the marker to determine anumber of tracks written during the adaptive self-servowrite process,ascertaining an appropriate formatting based upon the determined numberof tracks indicated by the marker and formatting the recording surfaceaccording to the ascertained format.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and form a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to accompanying descriptive matter, in whichthere are illustrated and described specific examples of an apparatus inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a storage system according to the present invention;

FIG. 2 is an illustration of one example of a magnetic disk drivestorage system;

FIG. 3 shows a diagram of a portion of a recording medium;

FIG. 4 shows the major components of a self-servowriting disk driveaccording to the present invention;

FIG. 5 illustrates a cross-sectional view of a disk layout according tothe present invention; and

FIG. 6 illustrates a flow chart of the method for providing adaptiveformatting via a self-servowrite process according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the exemplary embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration the specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized as structural changes may be made withoutdeparting from the scope of the present invention.

The present invention provides a method and apparatus for providing amarker for adaptive formatting via a self-servowrite process. The markis used later in the drive manufacturing process to identify the numberof tracks written on the surface and thus determine the appropriateformat to use in the drive.

FIG. 1 illustrates a storage system 100. In FIG. 1, a transducer 110 isunder control of an actuator 120. The actuator 120 controls the positionof the transducer 110. The transducer 110 writes and reads data onmagnetic media 130. The read/write signals are passed to a data channel140. A signal processor 150 controls the actuator 120 and processes thesignals of the data channel 140. In addition, a media translator 160 iscontrolled by the signal processor 150 to cause the magnetic media 130to move relative to the transducer 110. The present invention is notmeant to be limited to a particular type of storage system 100 or to thetype of media 130 used in the storage system 100.

FIG. 2 is an illustration of one example of a magnetic disk drivestorage system 200. As shown in FIG. 2, at least one rotatable magneticdisk 220 is supported on a spindle 222 and rotated by a disk drive motor224. The magnetic recording media on each disk 220 is in the form of anannular pattern of concentric data tracks (not shown).

At least one slider 226 is positioned on the disk 220, each slider 226supporting one or more magnetic read/write heads 228. As the disk(s) 220rotate, slider 226 is moved radially in and out over disk surface 230 sothat heads 228 may access different portions of the disk 220 wheredesired data is recorded. Each slider 226 is attached to an actuator arm232 by means of a suspension 234. The suspension 234 provides a slightspring force, which biases slider 226 toward the disk surface 230. Eachactuator arm 232 is attached to an actuator 236. The actuator 236 may bea voice coil motor (VCM). The VCM has a coil movable within a fixedmagnetic field, the direction and speed of the coil movements beingcontrolled by motor current signals supplied by a control unit 240.

During operation of the disk drive 200, the rotation of the disk 220generates an air bearing between slider 226 and the disk surface 230,which exerts an upward force or lift on the slider 226. The surface ofthe slider 226, which includes head 228 and faces the surface of disk220, is referred to as an air-bearing surface (ABS). The air bearingthus counter-balances the slight spring force of suspension 234 and,during normal operation, supports the slider 226 off of, and slightlyabove, the disk surface 230 at a small, substantially constant spacing.

The various components of the disk drive 200 are controlled in operationby control signals generated by a control unit 240, such as accesscontrol signals and internal clock signals. Typically, control unit 240has logic control circuits, storage apparatus, and a microprocessor. Thecontrol unit 240 generates control signals to control various systemoperations such as drive motor control signals on line 242 and headposition and seek control signals on line 244. The control signals online 244 provide the desired current profiles to optimally move andposition the slider 226 to the desired data track on the disk 220. Readand write signals are communicated to and from read/write heads 228through recording channel 246.

The above description of a typical magnetic disk drive storage system200 is provided for representation purposes only. It should be apparentthat disk storage systems may contain a large number of disks andactuators, and that each actuator may support a number of sliders. Manyother variations of the basic typical magnetic disk drive storage system200 may be used in conjunction with the present invention while keepingwithin the scope and intention of the invention. However, those skilledin the art will recognize that the present invention is not meant to belimited to magnetic disk drive storage systems as illustrated in FIG. 2.

FIG. 3 shows a diagram of a portion of recording medium 326 illustratingthe division into a number of propagation tracks 311, 312, 313, etc. aswell as a division of each track into a number of sectors, with a firstsector 301 typically coming immediately after the disk rotation index asdetermined either by an index pulse from the disk spindle motor driveror from the timing controller. Each sector is further divided into aregion 303 containing the amplitude bursts for propagation and a region304, which is reserved for the use of the precision timing propagationsystem and for writing the actual product servo pattern including sectorID fields and either amplitude burst or phase encoded patterns.Propagation burst areas 303 may be overwritten with user data followingservowriting. All of region 304 except for the part containing theproduct servo pattern will also be overwritten with user data. Eachpropagation burst region is further divided into a number of slots305-310 within which the amplitude burst patterns (A,B,C,D,E, and F) forpropagation are written. In FIG. 3, the propagation track pitch is shownas one quarter of the assigned data track width. For example, if thefirst user data track is chosen to be centered on propagation track 312,the next data track would be centered on propagation track 316, and soon across the disk. Other ratios of propagation to data track pitch canbe used, but the 4:1 ratio shown allows fine adjustment of the timing ofgrey code bits and phase encoded product servo patterns.

Typically, the data track pitch is chosen to be slightly larger than thetransducer write width so the edges of adjacent data tracks do notoverlap. This can be seen in FIG. 3 by noting the relative radiallocations of B and F bursts since these correspond to theabove-mentioned choices of data tracks centered on propagation tracks312 and 316 respectively. The propagation burst pattern shown consistsof a repeating sequence of 6 bursts. This is useful because the burstsin each slot do not overlap along the radial direction thereby allowingthe recording transducer to back up and read previously written bursts.The minimum number of slots required for propagation without suchchecking is 2. While the above description has been provided to show thedata tracks and the servo functions, those skilled in the art willrecognize that the present invention is not meant to be limited to theconfiguration shown.

FIG. 4 shows the major components of a self-servowriting disk drive 400according to one embodiment of the present invention. A disk drive 420with its recording transducer 422, voice coil actuator 424, recordingmedium or disk 426, and read/write control electronics 428, is connectedto a time delay unit 431 in series with a pattern generator 430, whichis clocked by a timing controller 432 that allows bursts of magnetictransitions to be recorded at precisely controlled times.

A readback signal from a file read/write electronics circuit 428 isconnected to an amplitude demodulator circuit 434, the output of whichis converted to digital form by an analog to digital converter (ADC) 436at times determined by timing controller 432 acting in concert with amicroprocessor sequence controller 433. Sequence controller 433 alsoaccesses a memory 438 for storage and retrieval of digitized readbackamplitudes used by a divider 440. Sequence controller 433 with memory438 also provide for the storage and retrieval of reference table valuesused by a subtracter 442 in creating the position error signal (PES)that serves as the input to a digital servo controller 444. Sequencecontroller 433 also provides computation capabilities for general use indetermining modifications to the stored reference table values and fordetermining appropriate delay settings to be applied to timing delayunit 431, and producing control signals for pattern generator 430.

The output of digital servo controller 444 is converted to analog formby a digital to analog converter (DAC) 446, and is further amplified andconverted to a current by a VCM driver 448. The driver current 450 isapplied to voice coil motor (VCM) 424 in the disk file causing recordingtransducer 422 to move approximately radially with respect to recordingmedium 426. The functions of divider 440, subtracter 442, and digitalservo controller 444 may be all achieved through the appropriateprogramming of microprocessor sequence controller 333.

FIG. 5 illustrates a cross-sectional view of a disk layout 500 accordingto the present invention. In FIG. 5, a mark (SSW mark) 510 is added atthe end of the adaptive self-servowrite process. The SSW mark 510 iswritten as a sequence of N-tracks at the outer edge 512 of the recordingsurface 513 just inside ramp 516. When the drive is turned off and theslider is not flying, the slider lands on ramp 516 disposed adjacent theload/unload zone 514 outside the disk and rests till the next power-oncycle. The SSW mark 510 is used later in the drive manufacturing processto identify a number of tracks written on the surface 513 and thusdetermine the appropriate format to use in the drive. The pattern forthe SSW mark 510 is unique and easily recognizable by the demodulator ofthe servo controller 444 of FIG. 4.

Alternatively, the drive may utilize a Contact Start Stop (CSS) mode.While the disk is stopped, the head contacts the disk. When the diskbegins rotation, the head floats. When the disk stops rotating, the headcontacts the disk again, thus the name Contact Start Stop (CSS) mode. InCSS mode, the head is put in an unstable floating state and slides andwears the disk surface each time the disk starts or stops rotating.Accordingly, some storage systems designed to perform CSS in an area(CSS zone or load/unload zone such as illustrated as 514 in FIG. 5)separate from the data area so as to prevent damage to the data areaduring CSS. Further, the SSW mark 510 could be placed at anypredetermined position, such as the inner edge of the recording surface.

Referring to FIGS. 4 and 5, a special servo command is used by the servocontroller 444 at function test to look for the SSW mark 510. Once theSSW mark 510 is found, the servo controller 444 moves the head 422toward the inner edge 520, but just inside the edge of the SSW mark 510.At that location, the head reads the grey code servo address and then,based on this reading, calculates the number of available data tracks530. Once the number of available data tracks 530 is known, theappropriate format to be used during the adaptive format process can bedetermined. Thus, the present invention provides a reliable method toidentify the number of available tracks 530.

In FIG. 5, an overshoot area 534 of 243 tracks is provided at region A.The load/unload zone 514, i.e., region C, is approximately 3.7% of thetotal number of tracks 530. Thus, knowing the total number of tracks, asprovided by the SSW mark 510, allows a calculation of the number of datatracks in region B 540 and the number of tracks in the load/unload zone514 of region C. From the total number of tracks 530, the appropriateformat may be used during the adaptive format process.

FIG. 6 illustrates a flow chart 600 of the method for providing adaptiveformatting via a self-servowrite process according to the presentinvention. In FIG. 6, an adaptive self-servowrite process is performedto write a variable number of tracks to a recording surface 610. Amarker is written at a predetermined location on the recording surface,wherein the marker indicates the number of tracks written during theadaptive self-servowrite process 620. Prior to formatting, the marker islocated 630 and processed to determine number of tracks written duringthe adaptive self-servowrite process 640. Based upon the determinednumber of tracks indicated by the marker an appropriate formatting isascertained 650. The recording surface is formatted accordingly 660.

Referring again to FIG. 4, the process illustrated with reference toFIGS. 5-6 may be tangibly embodied in a computer-readable medium orcarrier, e.g. one or more of the fixed and/or removable data storagedevices 468 illustrated in FIG. 4, or other data storage or datacommunications devices. A computer program 490 expressing the processesembodied on the removable data storage devices 468 may be loaded intothe memory 492 or into the servo controller 444, e.g., in a processor(not shown), to configure the servo controller 400 of FIG. 4, forexecution. The computer program 490 comprise instructions which, whenread and executed by the servo controller 444 of FIG. 4, causes theservo controller 400 to perform the steps necessary to execute the stepsor elements of the present invention.

The foregoing description of the exemplary embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not with this detailed description, but rather bythe claims appended hereto.

1. A method for providing adaptive formatting via a self-servowriteprocess, comprising: performing an adaptive self-servowrite process towrite tracks to a recording surface; writing a marker at a predeterminedlocation on the recording surface, the marker indicating the number oftracks written during the adaptive self-servowrite process; prior toformatting, locating the marker; processing the marker to determine anumber of tracks written during the adaptive self-servowrite process;ascertaining an appropriate formatting based upon the determined numberof tracks indicated by the marker; and formatting the recording surfaceaccording to the ascertained format.
 2. The method of claim 1 whereinthe writing a marker further comprises writing a marker toward an inneredge of the recording surface.
 3. The method of claim 1 wherein thewriting a marker further comprises writing a marker toward an outer edgeof the recording surface.
 4. The method of claim 1 wherein a ramp isdisposed adjacent an outer edge of the recording surface, and whereinthe writing a marker toward the outer edge of the recording surfacecomprises writing the marker just inside the ramp.
 5. The method ofclaim 1 wherein the writing a marker further comprises writing a greycode servo address indicating the number of tracks written during theadaptive self-servowrite process.
 6. The method of claim 1 wherein theprocessing the marker to determine a number of tracks written during theadaptive self-servowrite process further comprises processing the markwith a servo demodulator.
 7. The method of claim 1 wherein the locatingthe marker further comprises performing a servo command requesting themark be located during a function test.
 8. A servo written recordingmedium, comprising a number of tracks written during an adaptiveself-servowrite process and a marker disposed at a predeterminedlocation on the recording surface, wherein the marker indicates thenumber of tracks written during the adaptive self-servowrite process. 9.The servo written recording medium of claim 8 further comprising a rampdisposed at an outer edge of the recording medium.
 10. The servo writtenrecording medium of claim 9 wherein the marker is located toward theouter edge of the recording surface just inside the ramp.
 11. The servowritten recording medium of claim 8 wherein the marker is located towardan outer edge of the recording surface.
 12. The servo written recordingmedium of claim 8 wherein the marker is located toward an inner edge ofthe recording surface.
 13. The servo written recording medium of claim 8further comprising a grey code servo address at the marker for use indetermining the number of tracks written during the adaptiveself-servowrite process.
 14. The servo written recording medium of claim8 wherein the number of tracks indicated by the marker is associatedwith a predetermined formatting for the recording medium.
 15. A storagesystem for providing adaptive formatting via a self-servowrite process,comprising: a moveable storage medium having a recording surface forstoring data thereon; a motor for causing movement of the moveablestorage medium; an actuator assembly having an actuator arm and a sensordisposed at a distal end of the actuator arm, the sensor for reading andwriting data on the disk; a servo controller, operatively coupled to theactuator assembly and sensor, the servo controller providing a drivesignal to the actuator assembly for moving the actuator arm relative tothe recording medium, the servo controller performing an adaptiveself-servowrite process to write a number of tracks to a recordingsurface, writing a marker at a predetermined location on the recordingsurface, the marker indicating the number of tracks written during theadaptive self-servowrite process, prior to formatting, locating themarker, processing the marker to determine number of tracks writtenduring the adaptive self-servowrite process, ascertaining an appropriateformatting based upon the determined number of tracks indicated by themarker and formatting the recording surface according to the ascertainedformat.
 16. The storage system of claim 15 wherein the servo controllerwrites the marker toward an inner edge of the recording surface.
 17. Thestorage system of claim 15 wherein the servo controller writes themarker toward an outer edge of the recording surface.
 18. The storagesystem of claim 15 wherein a ramp is disposed adjacent an outer edge ofthe recording surface, the servo controller writing a marker toward theouter edge of the recording surface just inside the ramp.
 19. Thestorage system of claim 15 wherein the marker is written by the servocontroller toward an outer edge of the recording surface just inside aramp.
 20. The storage system of claim 15 wherein the marker furthercomprises a grey code servo address indicating the number of trackswritten during the adaptive self-servowrite process.
 21. The storagesystem of claim 15 further comprising a servo demodulator for processingthe grey code servo address to ascertain the number of tracks writtenduring the adaptive self-servowrite process.
 22. The storage system ofclaim 15, wherein the number of tracks indicated by the marker beingassociated with a predetermined formatting for the recording medium. 23.An article of manufacture comprising a program storage medium readableby a computer, the medium tangibly embodying one or more programs ofinstructions executable by the computer to perform a method forproviding adaptive formatting via a self-servowrite process, the methodcomprising: performing an adaptive self-servowrite process to writetracks to a recording surface; writing a marker at a predeterminedlocation on the recording surface, the marker indicating the number oftracks written during the adaptive self-servowrite process; prior toformatting, locating the marker; processing the marker to determine anumber of tracks written during the adaptive self-servowrite process;ascertaining an appropriate formatting based upon the determined numberof tracks indicated by the marker; and formatting the recording surfaceaccording to the ascertained format.
 24. The article of manufacture ofclaim 23 wherein the writing a marker further comprises writing a markertoward an inner edge of the recording surface.
 25. The article ofmanufacture of claim 23 wherein the writing a marker further compriseswriting a marker toward an outer edge of the recording surface.
 26. Thearticle of manufacture of claim 23 wherein a ramp is disposed adjacentan outer edge of the recording surface, and wherein the writing a markertoward the outer edge of the recording surface comprises writing themarker just inside the ramp.
 27. The article of manufacture of claim 23wherein the writing a marker further comprises writing a grey code servoaddress indicating the number of tracks written during the adaptiveself-servowrite process.
 28. The article of manufacture of claim 23wherein the processing the marker to determine number of tracks writtenduring the adaptive self-servowrite process further comprises processingthe mark with a servo demodulator.
 29. The article of manufacture ofclaim 23 wherein the locating the marker further comprises performing aservo command requesting the mark be located during a function test.